A lighting device which implements lighting by guiding light emitting from a light source has been variously required for a lamp for lighting, a lamp for vehicles, a liquid crystal display device and the like. In the lighting device, a technology for making the structure of equipment thin and a structure capable of improving the efficiency of light have been recognized as the most important technologies.
Hereinafter, as one example to which the lighting device is applied, a liquid crystal display device will be explained.
Referring to FIG. 1, a lighting device 1 is configured such that a flat light guide plate 30 is disposed on a substrate 20, and a plurality of side-view type LEDs 10 (only one being illustrated) are disposed on a side surface of the light guide plate 30 in an array shape. Light L incident to the light guide plate from the LEDs 10 is reflected upward by a fine reflection pattern or a reflection sheet 40 provided to a bottom surface of the light guide plate 30 and is radiated from the light guide plate 30. Then, the light is provided to an LCD panel 50 of an upper part of the light guide plate 30.
As illustrated in FIG. 2, the lighting device may be formed in a structure in which a diffuse sheet 31 or a plurality of optical sheets such as prism sheets 32, 33, a protective sheet 34 and the like are further added between the light guide plate 30 and the LCD panel 50.
Accordingly, the light guide plate is basically used as an essential component of the lighting device, but due to a thickness of the light guide plate, there is a limitation to make a thickness of a whole product thin. In the case of a large-sized lighting device, it is problematic that image quality is deteriorated.